Awhile ago my Ex started vibrating and thought it may have been a bearing. Adjusted the belt tension, blade tension and etc. But there was no way I was to tear the machine down knowing there's usually a simple answer to the problem. Contacted Ray at Seyci and within ten minutes corrected the vibration. On the back of top arm there's a 10mm nut on each side. Tightening each side the same smoothed the issue. Patience does help. By the way that's some fine cutting Dan.